1. Field of the Invention
The present invention relates to a suspension system of a conveying carriage or the like which runs by means of driven wheels, and more specifically, to a technique which can suppress, such as, inclination and vibration of the carriage while running.
2. Description of the Prior Art
Japanese First (unexamined) Patent Publication No. 5-170102 discloses a conventional suspension system of a conveying carriage. A structure of this suspension system will be explained with reference to FIG. 13.
In FIG. 13, a conveying carriage 1 includes a carriage body 11. A suspension system for the carriage body 11 includes compliance wheels 13a, 13b, 13c and 13d, a coupling plate 14 for coupling the compliance wheels 13a and 13b arranged laterally relative to the running direction of the carriage 1, and a coupling plate 15 for coupling the laterally arranged compliance wheels 13c and 13d. The suspension system further includes support bodies 131a, 131b, 131c and 131d for supporting the compliance wheels 13a.about.13d, and support bodies for supporting driven wheels 12a and 12b. The suspension system further includes vibration-proof means 16a, 16b, 16c and 16d provided between the coupling plates 14, 15 and the carriage body 11 at positions corresponding to the respective compliance wheels 13a.about.13d, and up/down slide mechanisms 17a, 17b, 17c and 17d extending vertically upward from the coupling plates 14 and 15 and provided between the coupling plates 14, 15 and four corners of the carriage body 11. The driven wheels 12a and 12b may also be mounted to the carriage body 11 using a coupling plate, vibration-proof means and up/down slide mechanisms.
According to the conventional suspension system, vertical vibration caused by loads of the carriage 1 is absorbed by the vibration-proof means 16a.about.16d and the up/down slide mechanisms 17a.about.17d, and the vibration proof means of the driven wheels 12a and 12b and the up/down slide mechanisms thereof. On the other hand, rocking motions and inclination of the carriage in the longitudinal and lateral directions can be reduced through the multiplier action of the coupling plates 14, 15 and the up/down slide mechanisms 17a.about.17d and of the coupling plate of the driven wheels 12a and 12b and the up/down slide mechanisms thereof.
However, according to the conventional suspension system, the laterally arranged compliance wheels 13a, 13b and 13c, 13d are coupled by the corresponding coupling plates 14 and 15, respectively. Accordingly, while the carriage runs on a running surface 18 having irregularities, such as, depressions, it is possible that one of the right and left compliance wheels is separated from the running surface 18. This may cause a posture of the carriage to be unstable, lowers the running linearity of the carriage and increases the vibration of the carriage.
Further, in general, the increment of carrying capacity of the carriage improves the production efficiency. Accordingly, when running on a carrying route where a start position and a stop position are fixed, it is required to increase a starting acceleration and a braking acceleration (deceleration) so as to allow the carriage to run at a high speed and for a long time. However, the increment of the starting and braking accelerations may increase the inclination and vibration of the carriage.